| Abstrakt: |
A pregnancy-test kit based on the principle of passive haemagglutination inhibition was used to assay antigen (»human chorionic gonadotrophin«) levels in 184 accurately timed urine samples collected during one 24-hour period from 24 pregnant women hospitalized for various clinical conditions.The precision of replicate assays was in the order of 20 per cent (standard deviation), that is, at the limit imposed by the dilution factor used.The antigen excretion rate (IU-eq./d), the antigen concentration (IU-eq./ml), and the fluid excretion rate (ml/d) all showed a diurnal rhythm, but shape, amplitude and phase of the average curves were different for the three parameters. Concentration varied inversely with fluid volume (r2= 0.47); the antigen excretion rate was not correlated with the latter (r2= 0.04). The concentration in morning urine was well correlated with the antigen excretion rate determined from the 24-hour pool (r2= 0.77). Variation between and within individuals was considerable with respect to all the relationships observed, and if these were disregarded, the distribution of the pooled data was approximately lognormal both for the concentrations and the excretion rates expressed as per cent of the corresponding 24-hour values.If antigen excretion were estimated, instead of from 24-hour collections, from (a) timed random collections, or (b) untimed morning urines, or (c) untimed random samples, changes in antigen excretion would have to be at least (a) 2–4 times, or (b) 2.5–6 times, or (c) 3–9 times greater, respectively, in order to be detectable in spite of diurnal variation. |
